Gyroscopic instrument



1948- Q F. D. BRADDON ET AL 0,

GYROSCOPIC INSTRUMENT Filed Oct. 8, 1943 2 Sheets-Sheet l INVENTORS: F. -D. B RADDON THEIRATfORNEY F. BRADDON ET AL GYROSCOPIC INSTRUMENT 2 Sheets-Sheet 2 Filed Oct. 8, 1943 NTORS:

F. RADD THEIR AT'T RNEY Patented Oct. 12, 1948 GYROSCOPIC INSTRUMENT Frederick D. Braddon,

Frederick Beach, Port signors to The tion of Delawar Babylon, and Lennox Washington, N. Y., as- Sperry Corporation, a corporae Application October 8, 1943, Serial No. 505,512

11 Claims.

This invention relates to gyroscopic instruments and more particularly pertains to a mounting for the rotor case of such an instrument by which a condition of gimbal lock is prevented.

The primary feature of the present invention resides in the provision of an auxiliary gimbal for carrying the gyro rotor case with releasable means between the case and auxiliary gimbal in the form of a coupling that normally locks the named parts together.

A further feature of the invention is provided by a coupling mechanism for the auxiliary gimbal and gyro rotor case that is released under the control of the main gimbal of the instrument.

Another feature of the invention resides in the means provided for controlling the horizon bar of a gyroscopic artificial horizon designed to provide full freedom in all axes as in an instrument of this character.

Other features and structural details of the invention will be apparent from the following description when read in relation to the accompanying drawings, wherein Fig. 1 is a front elevation view of a gyroscopic instrument of the artificial horizon type in which the present invention is embodied.

Fig. 2 is an enlarged plan view of the interior of the instrument.

Fig. 3 is a side elevation view of the parts illustrated in Fig. 2.

Fig. 4 is a further enlarged detail side elevation of one of the forms of coupling means shown herein between the rotor case and the auxiliary gimbal of the instrument.

Fig. 5 is a side elevation view of the coupling illustrated in Fig. 4 taken at right angles to the showing thereof in the previous figure.

Fig. 6 is a view similar to Fig, 4 with the main gimbal tipped out of a normal position, the same showing the manner in 'which the coupling is released.

Fig. 7 is a plan view, partly in section, showing a modified form of coupling means.

Fig. 8 is a side elevation view of the coupling illustrated in Fig. 7.

Fig. 9 is an enlarged detail view of the coupling as shown in Fig. 8, and

Fig. 10 is a side elevation view showing the interior of a gyroscopic instrument of the directional gyro type in which the present inventive concepts are embodied.

With reference to the artificial horizon form of gyroscopic instrument shown in Figs. 1 to 3,

inclusive, a gyro rotor I0 whose spin axis is normally vertical is mounted within a rotor bearing case II of conventional construction. In accordance with the teaching of the present invention, the rotor case is supported within the casing I2 of the instrument by means of a main gimbal I3 and an auxiliary gimbal I 4 in the novel manner hereinafter described. As shown in Fig. 2, the major axis of the bearing case It] on the main gimbal is defined by the bearings l5, I5, the axially spaced outer races of which are located in a frame I76 that is fixed to the outer casing I2. Gimbal I3 is U-shaped and the open position thereof is disposed adjacent the window I! in the front wall of the casing I2 for the instrument.

The auxiliary gimbal I 4 is pivotally mounted in the main gimbal by means of bearings I8, I8, and the rotor case I i is pivotally mounted on the auxiliary gimbal by means of bearings I9, I9. As shown, the major axis of the case on the auxiliary gimbal I l, bearings I8, I8, corresponds with the minor axis of the case, also defined by bearings I8, I8, on the main gimbal I3. Also, the minor axis of the case II on the auxiliary imbal defined by bearings I9, I9, normally corresponds with the major axis of the case on the main gimbal. It will be understood that the major axis of a gimbal supported rotor case is the axis of the gimbal; i. e., the major axis of case I 0 on main gimbal i3 is defined by the bearings I5, I5 and the major axis of case I!) on auxiliary gimbal I l is defined by the bearings I8, I 8. Further, the minor axis of the rotor case It) is the axis of the case within the gimbal; i. e., the minor axis of case In on main gimbal I3 is defined by bearings l8, I8 and the minor axis of the case on auxiliary gimbal I4 is defined by bearings I9, I9. From the above it is clear that the axis defined by bearings I8, I8 is considered as a major axis of support of the case with regard to auxiliary gimbal l4 and is also considered as a minor axis of support of the case with regard to the main gimbal I3. Relative to the gimbal axes per se, the axis of main gimbal I3 is defined by bearings I5, I5. Further, the axis of auxiliary gimbal I4 is defined by bearings I8, I8. The axis of the rotor case It! on gimbal I 4 is defined by bearings I9, I9, this axis normally corresponding with the axis of the main gimbal as clearly shown in Figs. 2 and 3. In accordance with the teaching of the invention, a releasable coupling as generally indicated at 2B is employed between the rotor case and auxiliary gimbal, Coupling 20 functions to normally look the case to the auxiliary gimbal so that no movement of the case relative to the auxiliary gimbal about the axis defined by bearings I9, I 9' can occur. With the case and auxiliary gimbal locked together, the case is universally supported by the main gimbal I3. Mutually perpendicular, major axis defined by bearings I5, I5 and minor axis defined by bearings I8, I8 provide this normal universal mounting for the case. With this type of gyroscopic instrument upon pitch of the craft on which the instrument is mounted the casing I2 may move about the athwartship axis of the craft to a position in which the main gimbal axis defined by bearings I5, I5 is coincident with the 'bearing 18 is fixed in spin axis of the gyro rotor as indicated at 2| in Fig. 3. This condition, known as gimbal lock, is prevented in the improved instrument by means of the auxiliary gimbal I4 and the coupling 20 which cooperate in described.

As particularly shown in the form of coupling means illustrated in Figs. 4 to 6, inclusive, a stub shaft 2| is fixed to the main gimbal l3. At the end of the fixed shaft 2! is located a holding piece 22 for two, arcuate slot defining, resilient arms 23 and 24. particularly shown in Fig. 5. The inner race for 2!. The other part of the coupling means shown in Figs. 4 to 6, inclusive, is a pin from and is fixed to the rotor case II.

which frictionally engage resilient springs 23 and 25, as particularly shown in Fig. 4 to normally secure the case from movement about the auxiliary gimbal axis thereof definedbybearings l9, ii),

In accordance with the teaching of the present vention, the coupling means is released under control of the main gimbal i3 when the latter becomes inclined through a approaching 90. If the major axis 55, i is placed fore and aft, as is usual, the cause of the condition shown in Fig. 6 would be a steep dive, of the craft. When the instrument thus tilts: about a pitch axis the main gimbal l3 moves out of a horizontal plane about axis i8, it. This causes corresponding movement of the holding piece 22 and the arms thereon so that the straight. sided pin 25 no longer held in a locked condition. Thus, when the inclined through a substantial angle approach-3 ing 96 which would otherwise cause gimbal lock,

the rotor case is then universally supported with. the auxiliary gimbal on axes:

in the casing on i8, i8 and i9, i3. Spring means '28 between the trunnion of the case i l and gimbal 54 effects:

movement of the case about axis i9, is to ro store the coupling to a normal locking condition.-

he resilient arms 23 and E i are curved ,to per-- mitthe parts of the coupling to slide over each other if necessary in effecting their engagement as the: main gimbal returns to a normal position with the case freefrom tilt about the axis 8.19.

In the instrument shown, he rotor is air driven and the rotor case is pneumatically erected by suitable means well, knownin the art and, with which this inventive subject matter isnotconcerned. The pendulous shutters shown on the case H in Fig. 3 provide the. conventional erection controls for the instrument.

To obtain an artificial horizon indication from the described type of gyroscopic instrument, horizon bar 29 is employed. Bar 28isobserved with reference to pitch indices BS-located onthe window ll of the casing 12 oi- .the. instrument. A mask 3! is fixed to the front of the auxiliary gimbal i i behind the window and the: observed portion of the bar 29 which conceals the interior parts of the instrument from observation. Roll indices 32'may be fastened to the maslQBi, the same being observed with reference to a scale; 33 on the window 1 i of the instrument.

In accordance with the teachingof the present invention, a mechanism that. is positioned.by the auxiliary gimbal is employed to controlthe horizon bar 25. As shown, this mechanism includes; a first pinion 34 that is fixedon the, ex-

the manner hereinafter position on the stub shaft 25 that extends. Pin 255 is constructed to include cam surfaces 26 and 21* they arcuate ends of the;

substantial angle main gimbal becomes Arms 23 and 24 are curved as i trically located on the pinion 38 engages a longttudinal slot 39 in the horizon bar.

The horizon bar 29 is pivotally mounted on the main gimbal as indicated at 48. In the improved bar mechanism provided, the meshing gears or pinions 34, 36 havea 2 to 1 gear ratio. Such ratio is required in order to maintain pin 38 in a uniform normal position in the slot 39 in order to obtain a correct indication from the'bar both when the-casing l2 of the instrument as viewed in Fig. 3 is turned 180,about the pitch axis of the, instrument or axi of the auxiliary gimbal ring l4 and when the main gimbal is displaced inpositionabout-its axis 180 from the position in which it is shown in Fig. 2. The improved artificial horizoninstrument is completely maneuverable about both roll and craft on which it is mounted.

A modified form of the couplingmeans is shown in Figs. 7, 8 and 9, in which the holding surfaces of the curved spring 23 and 24 can substantially surround a round pin 25 and thus increase the holding action of the couple over the type previously described. In the present couple the spring holding piece is axially movable so that the same moves away from the pin when the couple isreleased. A holding piece 22 is constructed to slide in a hollow trunnion il, the piece being pressed by a spring 42: within the trunnion so that the cam defining flange i3 is continuously urged against two balls &4

' that are located in respective brackets 45 fixed to the auxiliary gimbal I i. The flange has two opposite depressions thereinas indicated at -46, Fig. 8, by which the holding piece 22 is permitted to move to a position in which the springs-23, 24-

thereof engage the pin 25.. Piece 22" is held against rotation in the hollow trunnion 41' by a suitable axial groove and key connection between theparts. When the gimbal l3 moves out of a normal position, trunnion 4i. and holding piece 22 turn therewith. The cam defining flange also turns sothat the balls l l ride upon the high surface thereof and push the piece 22' further within the hollow trunnion against the action of the spring 42.- This-moves the holding springs out of engagement with the pin 25 to free the rotor case-l! so the same can move about its axis [9,19'.

Withrefer-ence to Fig.;10, a gyroscopic instrumentof the directionindicating type is shown incorporating the features of the present invention. The casingofthis instrument is indicated at 5%. Within the casing 5B,,a vertical ring Si is mounted to pivot about a vertical axis; the

ring having a compass card 52 thereon thatlis mally. preventingmovement of the case55. about the .ax-isdefined by bearings 55, 55. In this instance, the .coupling. 5l-is released .dueto movementof the casing-50; and ring..5l: ;about the pitch axes of the in the frontwalliof the in roll axis of the craft so that when the spin axis of the rotor in the case 55 which is normal to the plane of the paper as viewed in this figure becomes coincident with the axis of the Vertical ring 5|, the rotor case is universally supported on the auxiliary gimbal 53 on mutually perpendicular axes defined by bearings 56, 56' and bearings 54, 54.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A mounting for the rotor case of a gyro instrument comprising a main gimbal on which the rotor case is normally supported for universal movement about mutually perpendicular major and minor axes, an auxiliary gimbal carrying the rotor case and pivotally mounted on the main gimbal, the major axis of the case on the auxiliary gimbal corresponding with the minor axis of the case on the main gimbal and the minor axis of the case on the auxiliary gimbal normally corresponding with the major axis of the case on the main gimbal, and a releasable coupling between the rotor case and auxiliary gimbal normally looking the case and auxiliary gimbal together, said coupling being released by the main gimbal upon movement of the same relative to the auxiliary gimbal through a predetermined angle to prevent a condition of gimbal lock from occurring in the instrument.

2. A mounting as claimed in claim 1, including spring means between the rotor case and auxiliary gimbal eflective to move said rotor case towards its normally locked position.

3. A mounting as claimed in claim 1, in which said coupling includes a pin extending from the rotor case and an axially movable, holding piece mounted on the main gimbal, said holding piece and pin moving out of locking engagement to free the auxiliary gimbal.

4. Means for preventing a gimbal lock condition in a gyroscopic instrument having a rotor case, said means including a main gimbal, an

auxiliary gimbal carrying said case pivotally mounted on the main gimbal with the axes of the respective gimbals mutually perpendicular, and a coupling, one part of which is located on the case and the other part of which is situated on the main gimbal, that normally locks the auxiliary gimbal to the case, the connecting ends of the respective coupling parts being constructed to release the auxiliary gimbal from a locked condition when the main gimbal is inclined more than a predetermined amount from its normal position relative to the auxiliary gimbal.

5. A gyro vertical'instrument having, a casing, a main gimbal in said casing, an auxiliary gimbal pivotally mounted on said main gimbal, said gimbals being arranged with their respective axes mutually perpendicular, a gyro rotor case pivotally mounted on "said auxiliary gimbal with the axis thereof normally corresponding with the axis of the main gimbal, and a releasable coupling normally locking the case to the auxiliary gimbal, said coupling being released upon a substantial tilt of said main gimbal about the axis of the auxiliary gimbal.

6. A directional gyro instrument having a case ing, a ring pivotally mounted in said casing to move about a normally vertical axis, an auxiliary ring pivotally mounted on said first ring movable about a normally horizontal axis, a gyro rotor case pivotally mounted on said auxiliary ring with the axis thereof normally corresponding with the axis of the first ring, a coupling normally locking the case to the auxiliary ring, and means for releasing said coupling upon movement of said first ring relative to said auxiliary ring through a substantial angle.

7. A gyroseopic artificial horizon including a main gimbal pivotally mounted on a casing, an auxiliary gimbal pivotally mounted on said main gimbal, said gimbals being arranged with their respective axes mutually perpendicular, a gyro rotor case pivotally mounted on said auxiliary gimbal with its pivotal axis normally aligned with the axis of the main gimbal, a horizontal bar pivotally mounted on the main gimbal, and mechanism driven by said auxiliary gimbal for controlling the horizon bar.

8. An instrument of the character claimed in claim 7, in which said mechanism includes a first pinion mounted on the trunnion of the auxiliary gimbal, and a second pinion with half the teeth of the first pinion having a pin thereon that engages a slot in the horizon bar, said pinions being in meshing engagement.-

9. An instrument of the character claimed in claim 7, which includes a releasable coupling be tween the case and the auxiliary gimbal that normally locks the case and auxiliary gimbal together.

10. A completely maneuverable gyroscopic artificial horizon having a gimbal mounted rotor case including a longitudinally slotted horizon bar pivotally mounted in the gimbal, and mechanism for positioning the bar comprising first and second engaged gear means having a 2 to 1 gear ratio, the first and larger of which is positioned by the rotor case and the second and smaller of which is rotatably mounted on the gimbal, said second gear having a. pin engaging the slot in the horizon bar.

11. In a gyroscopic artificial horizon, a casing having a window with a roll scale thereon, a main gimbal therein, an auxiliary gimbal pivotally mounted on said main gimbal, said gimbals being arranged with their respective axes mutually perpendicular and normally horizontal, a gyro rotor case pivotally mounted on said auxiliary gimbal with the axis thereof normally corresponding with the axis of the main gimbaL'and a roll index cooperating with the scale mounted on said auxiliary gimbal.

FREDERICK D. BRADDON. LENNOX FREDERICK BEACH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Murtagh et al Jan. 8, 1946 Certificate of Correction Patent No. 2,450,875. October 12, 1948. FREDERICK D. BRADDON ET AL. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 20, claim 7, for the word horizontal read horizon;

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 17th day of May, A. D. 1949.

THOMAS F. MURPHY,

Assistant Oommz'ssz'oner of Patents. 

